SOLUTION: Determine the equation of combined variation. Then solve for the missing value. x varies directly with y and inversely with z. x=125 when y=5 and z=4. Find x when y=4 and z=5.

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Question 325771: Determine the equation of combined variation. Then solve for the missing value.
x varies directly with y and inversely with z.
x=125 when y=5 and z=4.
Find x when y=4 and z=5.
I understand that z=kxy, tried to plug this in and work it, but I think I may be doing it wrong. Should I be using z=kxy? If so show work so that I may understand where I went wrong. Thanks
Found 2 solutions by jim_thompson5910, solver91311:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
The equation should be x=%28ky%29%2Fz. Let me know what you get.

Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


Your understanding is a bit askew. "x varies directly as y and inversely as z" means:



Here's how you do it:

Something varies directly as something else.

Write the something, write "=", write "k", write the something else.

Something varies inversely as something else.

Write the something, write "=", write "k", write the something else IN THE DENOMINATOR.

So:









Hence:



Now if and then



John